Accessibility Color Wheel
Accessibility Color Wheel Version 2.0 by Giacomo Mazzocato. This is a very useful tool to test colour contrast and visibility for people with different types of colour blindness.
4096 Color Wheel
4096 Color Wheel Version 2.1 by Jemima Pereira. Shows the closest web-safe, web-smart and unsafe colours. Gives the hexadecimal code for colours.
The web-smart colours are those 4096 colours composed of any three pairs of identical hexadeximal digits (0-9 and a-f), such as #dd1188. Remember that these colours can be coded in a short-hand form, e.g. #d18 means the same as #dd1188.
ColorPicker
ColorPicker 3.0 by Joe Barta. Select from 4096 web-safe and web-smart colours. Generate style sheet code for background, text and link states.
ColorBlender
The ColorBlender creates a set of six colours that blend well in a palette. Gives both hexadecimal and RGB colour values. Blends can be saved for future use.
Color Scheme Designer
Color Scheme Designer creates a sets colours that blend well in a palette. Gives both hexadecimal and RGB colour values. Can lighten or darken the selected scheme. Shows visibility for people with different types of colour blindness.